Cooling system for internal combustion engines



April 8, 1941. F. NALLINGER 2.237.910

COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Sept. 27; 1938 if l a FRITZ NALLINGER BY: 'Jfttormays Patented Apr. 8, 1941 COOLING SYSTEM no I no R INTERNAL COMBUS- N ENGINES Fritz Nallinger, Stuttgart, Germany, assignor to Daimler-Benz Aktiengesellschaft,

Stuttgart- Unterturkheim, Germany Application September 27, 1938, Serial No. 231,860

1 In Germany September 15, 1937 11 Claims.

This invention relates to a cooling system for internal combustion engines especially aircraft engines, and consists substantially in that-the liquid circulating in an, internal cooling circulation and directly cooling the engine is conducted to a heat exchanger, in which it gives up the heat to the liquid of a second, external cooling circulation in which the main radiator, for example subjected to the air current, is located. A liquid is used for the internal circulation, the boiling point of which is higher under working conditions of the system than the highest temperature occurring during the working of the system. Water under superpressure or another liquid under pressure and under this condition with a boiling temperature above 100 C. or a hot cooling agent, which may be mixed with compartments under pressure and surfaces of the internal cooling circulation may be kept very water, is therefore used as cooling liquid of the ,4 internal circulation and a liquid not under superpressure, 11. e. under atmospheric pressure, preferably a hot cooling agent such as glycol, is used as cooling liquid for the external circulation. But water may also be used'for the external circulation. It is only necessary that the cooling liquid for the external circulation does not boil under atmospheric pressure under working conditions. in case e. g. of water suitable means therefore must be provided, e. g. the size of the external radiator must be chosen correspondingly large.

As hot cooling agents furthermore mineral oils or glycerine may be used.

By the invention the advantage of a high cooling agent temperature is attainable on the one hand and on the other hand at the same time the disadvantage of the hitherto known hot cooling systems is avoided. For example the engine cooling with glycol, owing to the'bad heat transition and the lesser specific heat of the glycol, possesses the disadvantage of a relatively low cooling eifect. If, however, exclusively water subjected to pressure whose boiling temperature exceeds 100 C. is used for cooling, large heavy radiators are necessary to withstandthe water pressure and nevertheless have a sufficiently large surface exposed to the air. Furthermore, such radiators, owing to their large size, are particu larly exposed to the danger of damage (for example damage by bullets) and particularly susceptible-to such damages as, in the event or a sudden change in the cooling water pressure, steam explosions may occur. 5

As compared herewith the invention possesses the following advantages in addition to the advantage of a great drop in heat known in connection with cooling with hot cooling agents; the

small, so that the circulation is easier to keep free from leakage and less exposed to the danger of damage. The heat exchanger transmitting the heat from the internal to the external cooling circulation, being flushed'with liquid on both sides, can be very small and, being not dependent upon the air current, can be arranged protected in such a manner that the danger of damage is reduced to a minimum. On the other hand an ordinary radiator may be used for the external cooling circulation so that an ample heat radiation to the air can take place even when using glycol or other hot cooling agents. If the external cooling circulation is damaged, the consequences, owing on the one hand to the normal pressure prevailing therein, are less serious than in the case of damage to a cooling cir culation under high pressure, and on the other hand the engine can still be run with the internal cooling circulation, although at a decreased efificiency, so that, for example, when i used on aircraft, an emergency landing can be carried out in any case.

Advantageously the heat exchanger, in which both cooling mediums are circulating, is provided with special protection against extemal damages.

Two embodiments of the invention are illustrated diagrammatically by way of example on the accompanying drawing,

Fig. i being a side elevation of a cooling system embodying the invention applied to an internal combustion engine.

'Fig. 2, a modification, and

Fig. 3, a vertical section of the heat exchanger of Fig. 1 disclosing structural detail. I

a designates the engine (in Fig. 1 an engine with cylinders in row formation), b the heat exchanger, e the inflow of the liquid of the internal cooling circulation to the heat exchanger, d the outflow and c a cooling water pump which is preferably interposed and which returns the cooling liquid to the cooling jacket of the en gme.

As cooling liquid for the internal cooling circulation for example superheated water is used whose boiling point is about C. at 2 atms. and about 133 C. at 3 atms. The heat exchanger may be of any desired type. In. the drawing the liquid of the internal cooling circulation is con ducted through a system of pipes ,f of the heat exchanger which system is flushed by the liquid of the external cooling circulation.

The latter is formed by the jacket space g of the heat exchanger, of the conduit h the outer radiator i and the return conduit k. A pump 1 is preferably arranged in the return conduit and effects the circulation of the cooling agent in the external cooling system. As cooling agent ordinary water may be used in this instance or also a hot cooling agent such as glycol, the cooling agent being preferably not under pressure.

Fig. 2 shows by way of example the application of the invention to an engine with. cylinders in V-formation. The heat exchanger is in this instance arranged between the cylinders. The radiator for the external circulation of the cooling agent is there preferably arranged above the heat exchanger forming a bridge as shown in the drawing. Otherwise the arrangement is the same as in the example illustrated in Fig. 1. A circulating pump may also be provided in the external cooling circulation system bhlk. The pumps e and l of the two circulating systems may, if necessary, be combined to form a common aggregate.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed I claim:

1. In a cooling system for internal combustion engines comprising an internal combustion engin, a heat exchanger, an air-cooled radiator, pipes connecting the upper and the lower part of the air-cooled radiator with one part of the heat exchanger so as to cool the latter by a medium exposed to atmospheric cooling, pipes connecting the upper and lower part of the engine with the other part of the heat exchangenthe coolin system of the engine being filled with a liquid, the boiling point of which is under working conditions higher than the highest working temperature, the cooling system of the air-cooled radiator being filled with a hot liquid under atmospheric pressure, which is under working conditions in the liquid state.

2. In a cooling system for internal combustion engines comprising an internal combustion engine, a heat exchanger, an air-cooled radiator, pipes connecting the upper and the lower part of the air-cooled radiator with one part of the heat exchanger so as to cool the latter by a medlum exposed to atmospheric cooling, pipes connecting the upper and lower part ofthe engine with the other part of the heat exchanger, the cooling system of the engine being filled with a liquid, the boiling point of which is under working conditions higher than the highest working temperature, the cooling system of the air-cooled radiator being filled with a hot liquid under atmospheric pressure, being under working conditions in the liquid state, means to protect the heat exchanger against external damages, and a pump in the cooling system of the engine.

3. In a cooling system for internal combustion engines with cylinders in V-formation comprising an internal combustion engine, a heat exchanger placed in the space between the two rows of cylinders, an air-cooled radiator above the heat exchanger, thus forming a bridge over the upper parts of the two rows of cylinders, pipes connecting the upper and the lower part of the, radiator with one part of the heat exchanger, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, .he cooling system of the engine being filled with a liquid, the boiling point of which is under working conditions higher than the highest working temperature, the cooling system of the radi-v ator being filled with a liquid under atmospheric pressure, being under working conditions in the liquid state, means to protect the heat exchanger against external damages, and a pump in the cooling system of the engine.

4. In a cooling system for internal combustion engines comprising an internal combustion engine, a heat exchanger, an air-cooled radiator, pipes connecting the upper and the lower part of the air-cooled radiator. with one part of the heat exchanger so as to cool the latter by a medium exposed to atmospheric cooling, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with water under superpressure, the cooling system of the aircooled radiator being filled with a hot liquid cooling medium under atmospheric pressure.

5. In a. cooling system for internal combustion engines comprising an internal combustion engine, a heat exchanger, an air-cooled radiator, pipes connecting the upper and the lower part of the air-cooled radiator with one part of the heat exchanger so as to cool the latter by a medium exposed to atmospheric cooling, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with a hot liquid cooling agent, the cooling system of the radiator being filled with water under atmospheric pressure, means being provided to keep the temperature in this cooling system below C.

6. In a cooling system for internal combustion engines with cylinders in V-formation comprising an internal combustion engine, a heat ex.- changer placed in the space between the two rows of cylinders, an air-cooled radiator above the heat exchanger, thus forming a bridge over the upper parts of the two rows of cylinders, pipes connecting the upper and the lower part of the radiator with one part of the heat exchanger, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with a liquid, the boiling point of which is under working conditions higher than the highest working temperature, the cooling system of the radiator being filled with a liquid under atmospheric pressure, being under work-- ing conditions in the liquid state.

7. In a cooling system for internal combustion engines with cylinders in V-iormation comprising an internal combustion engine, a heat exchanger placed in the space between the two rows of cylinders, an air-cooled radiator above the heat exchanger, thus forming a bridge over the upper parts of the two rows of cylinders, pipes connecting the upper and the lower part of the radiator with one part of the heat'exchanger, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with water under superpressure, the cooling system of the radiator being filled with a hot cooling medium under atmospheric pressure, means to protect the heat exchanger against external damages, and a pump in the cooling system of the engine.

8. In a cooling system for internal combustion engines for aircraft machines comprising an internal combustion engine, a heat exchanger, an air-cooled radiator, pipes connecting the upper and the lower part of the air-cooled radiator with one part of the heat exchanger so as to cool the latter by a medium exposed to atmospheric cooling, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with a liquid, the boiling point of which is under working conditions higher than radiator above the heat exchanger, thus forming a bridge over the upper parts of the two rows the highest working temperature, the cooling system of the radiator being filled with glycol in liquid condition and under atmospheric pressure during operation.

9. In a cooling system for internal combustion engines for aircraft machines with cylinders in V-torrnation comprising an internal combustion engine, a heat exchanger placed in the space between the two rows of cylinders, an air-cooled radiator above the heat exchanger, thus forming a bridge over the upper parts of the two rows of cylinders, pipes connecting the upper and the lower part of the radiator with one part of the heat exchanger, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with a liquid, the boiling point oi which is under working conditions higher than the highest working temperature, the cooling system of the radiator being filled with glycol under atmospheric pressure, means to protect the heat exchanger against external damages, and a pump in the cooling system of the engine.

iii. In a cooling system for internal combustion engines for aircraft machines with cylinders in w iformation comprising an internal combustion engine, a heat exchanger placed in the space between the two rows of cylinders, an air-cooled of cylinders, pipes connecting the upper and the lower part of the radiator with one part of the heat exchanger, pipes connecting the upper and lower part of the engine with the other part of the heat exchanger, the cooling system of the engine being filled with a liquid, the boiling point of which is under working conditions higher than the highest working temperature, the cooling system of the radiator being filled with glycol under atmospheric pressure, means to protect the heat exchanger against external damages, two pumps being provided, one in the cooling system of the engine, the other in the cooling system of the radiator.

11. A cooling system for internal combustion engines, comprising an internal combustion engine, an air cooled member and a heat exchanger, one portion of said heat exchanger beair cooled member being filled with a hot liquid under atmosphericpressure that remains in the liquid state under the working conditions.

FRITZ NALLINGER. 

